In 4-quart saucepan, melt butter over medium heat. Stir in onions, grill seasoning and thyme. Cook 4 to 6 minutes, stirring frequently, until onion softens. Stir in flour; cook and stir 1 to 2 minutes or until mixture is deep golden brown. Stir in broth. Heat to boiling over high heat, stirring frequently. Boil and stir 1 minute. Remove from heat. Stir in cream cheese until melted. Stir in chicken and frozen mixed vegetables.